Undone by Brooke Taylor

When Kori Kitzler, the "dark angel" of the eighth grade, tells Serena Moore that they are more alike than she thinks, Serena is instantly intrigued. But after their friendship solidifies and a twist of fate yanks Kori away from Serena, she will need to find a way to complete her best friend's life left undone.

Brooke Taylor lives and writes from her country home in Oklahoma where her horses are a constant, but happy, distraction. Her first "real" job was as a Wrangler for a dude ranch. Since then she has worked for ski resorts in Colorado and traveled the high seas while living on cruise ships. Currently she works for a large public school district. Undone is her first novel.